1. Field of the Invention
The present invention relates to a liquid crystal display device and a fabricating method thereof. In particular, the present invention relates to a liquid crystal display device and a fabricating method thereof in which production yield is improved by preventing the defect of a gate line and a data line due to static electricity.
2. Description of the Related Art
A liquid crystal display device comprises a thin film transistor array substrate and a color filter array substrate which face each other with a liquid crystal material in between. The liquid crystal display device also comprises a driving circuit which provides driving signals for driving the liquid crystal material around the two array substrates.
The thin film transistor array substrate comprises gate lines and data lines which cross each other on a lower substrate, thin film transistors each formed on a crossing part of the data lines and gate lines, and pixel electrodes each connected to the corresponding thin film transistor. A driving signal is provided to the corresponding gate line and data line by the driving circuit. The driving circuit is connected to a gate pad formed at the end of the corresponding gate line and a data pad formed at the end of the corresponding data line and provides a driving signal to the gate and data line. The thin film transistor is turned on by a scan signal provided on the corresponding gate line and provides a pixel voltage signal which is provided on the corresponding data line to the pixel electrode.
The color filter array substrate comprises a black matrix which divides a cell area by forming on the area corresponding to the gate line and data line of the upper substrate, a color filter formed on the area partitioned by the black matrix, and a common electrode forming a vertical electric field to drive the liquid crystal material by facing with the pixel electrode formed on the lower substrate.
The thin film transistor array substrate further comprises a static electricity preventing element 8 which is formed on a non-display area surrounding a visible (display) area 10 to block the inflow of the static electricity into the data line (DL) and gate line (GL) disposed in the visible area 10, as shown in FIG. 1.
The static electricity preventing element 8 is connected between a common line (CL) supplied with a standard voltage for driving the liquid crystal and each data line (DL). The static electricity preventing element 8 guides the static electricity flowing into the data line (DL) through the data pad (DP) towards the common line (CL). In addition, the static electricity preventing element 8 connected between the common line (CL) and each gate line guides the static electricity flowing into the gate line (GL) through the gate pad (GP) towards the common line (CL).
The static electricity preventing element 8 comprises a plurality of transistor (T10, T20, T30) driven by a driving voltage higher than a TFT driving (or thresh-hold) voltage which is to select a pixel inside a pixel array area. The plurality of transistor (T10, T20, T30) are disposed on the edge of the pixel array area so that they are connected to the common line (CL). The transistors (T10, T20, T30) are turned on by the high voltage applied to the gate line or the data line when static electricity occurs. Therefore, they guide the over current due to the over-voltage of static electricity at the data and gate line to the common line (CL) which is grounded so as to have lower impedance. On the contrary, the transistors (T10, T20, T30) are not electrically connected to the common line (CL) under normal driving condition and has a high impedance of several MΩ and maintain the turned off status.
The static electricity preventing element 8 is equipped to protect elements of the substrate by discharging the high voltage which occurs during the manufacturing process of the substrate to the ground line. However, in case that high AC voltage static electricity occurs at the data pad (DP) or gate pad (GP), the transistors (T10, T20, T30) of the static electricity preventing element 8 are not turned on normally. As a result, the gate line (GL) or the data line (DL) is damaged as the high AC voltage static electricity flows into the data line (DL) or the gate line (GL) data and dim phenomenon occurs eventually. In other words, as a result, the liquid crystal display device becomes defective and production yield is degraded.